JP2012076281A - Production method of resin molded product having emboss - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a resin molded product having an emboss which does not easily generate white blurring, without requiring repairing of a molding mold and coating after molding.SOLUTION: When producing the resin molded product 1 having the emboss 2 on a prescribed surface by extrusion molding, the production method of the resin molded product has a relationship obtaining process which obtains a relationship of a rise angle θ from the bottom surface of a concave part 4 of a convex part 3 constituting the emboss 2 and the ratio of an unevenness average height r to the unevenness maximum height d of the emboss 2 with degree of the white blurring emerging on the emboss 2, respectively; an optimum value setting process which sets the rise angle θ from the bottom surface of the concave part 4 of a convex part 3, and the ratio of the unevenness average height r to the unevenness maximum height d of the emboss 2 in the range that the white blurring is not visible on the emboss 2, based on the relationship found in the relationship obtaining process; and an emboss designing process which designs the emboss 2 based on the values of θ, R (=r/d) having been set in the optimum value setting step.

Description

  The present invention relates to a method for manufacturing a resin molded product having a wrinkle, and more particularly to a method for manufacturing a resin molded product in which an appearance defect called white blur does not occur in a wrinkle.

  For example, when automotive interior parts such as instrument panels and garnishes are molded with resin, surface treatment called graining is performed on the mold for the purpose of improving the quality from the viewpoint of the design and preventing appearance defects such as sink marks. In many cases, it is applied to the molding surface of a mold, and a minute uneven pattern called grain is provided on the surface of a molded product molded by the mold.

  The wrinkle pattern and shape are appropriately set according to the characteristics (tactile sensation, gloss, etc.) required for the above-mentioned resin molded product, but the correlation between each required characteristic and the wrinkle specification has not been clarified yet. In fact, the actual situation is that the specifications of wrinkles are determined based on experience and intuition. On the other hand, an attempt has been made to clarify the correlation between the required characteristics and the specifications of the texture and to reflect them in the design for obtaining predetermined characteristics.

  For example, the following Patent Document 1 describes a method of setting a grain roughness that provides the most preferable tactile sensation from the relationship between the grain roughness that varies depending on the hardness of the resin material to be molded and a good tactile sensation. Alternatively, in Patent Document 2 below, the texture of the embossed surface is obtained so as to obtain a texture that has a glossy feeling or a high-class feeling and that can prevent the appearance defects such as welds, flow marks, sink marks, and unevenness from being noticeable. It describes a method for setting the interval, step, and conditions for blasting a molding die for embossing to an appropriate range.

JP 2000-229356 A Japanese Patent Laid-Open No. 11-320627

  By the way, in some resin molded products (interior parts such as instrument panels) provided with wrinkles, in addition to the above-mentioned defects in appearance, when the surface provided with wrinkles is seen from a certain direction, it looks white and blurred. It has been found that an appearance defect called “white blur” may appear. The term “white blur” as used herein means what appears due to a structural defect that has occurred in a molded product during injection molding. After molding a resin molded product, for example, when assembling with other parts, It is different from the whitened portion generated on the surface due to some impact or external force during use in the completed state.

  As a means for improving this kind of appearance defect (white blur), reworking of the molding die or painting treatment after molding can be considered, but the former is the mechanism of the occurrence of white blurring, Since there is no clear correlation between the specifications and the occurrence of white blurring, it is highly likely that a considerable amount of man-hours will be required to find the appropriate texture specifications. Further, the latter is contrary to the original purpose of providing a texture that imparts glossiness and luxury to the resin-molded surface without painting, and it is difficult to adopt because the man-hour increases accordingly.

  In view of the above circumstances, according to the present invention, it is possible to provide a method capable of easily producing a resin molded product having a texture that does not generate white blur without requiring reworking of a molding die or painting after molding. Technical issues to be solved.

  The solution to the above-described problem is achieved by the method for producing a resin molded product having a texture according to the present invention. In other words, this method of manufacturing a resin molded product, when producing a resin molded product having a texture on a predetermined surface by injection molding, the rising angle from the bottom surface of the convex portion constituting the texture and the maximum height of the uneven surface of the texture. A correlation acquisition step for acquiring a correlation between the ratio of the average height of the unevenness to the height and the degree of white blur appearing in the wrinkles, a rise angle from the bottom surface of the convex portion based on the correlation obtained in the correlation acquisition step, and , The optimum value setting process to set the ratio of the uneven height to the maximum uneven height of the wrinkle in a range where white blur is not seen in the wrinkle, and the wrinkle design to design the wrinkle based on the value set in the optimum value setting process And characterized in that it comprises a process.

  The present inventors have evaluated and examined the causal relationship between the specification of the grain and the occurrence of white blur, and it has been found that a predetermined correlation is recognized between the parameter relating to a specific grain shape and the occurrence of white blur. . That is, several types of parameters related to the wrinkle shape and wrinkle characteristics, specifically, the wrinkle depth (maximum height of the wrinkles constituting the wrinkle), the ratio of the average height of the wrinkles to the wavy maximum height, The sensory evaluation test evaluated the area ratio with the recess, the rising angle of the protrusion from the bottom of the recess, the presence or absence of white blurring when the gloss value was changed, and the correlation between these. As a result, it was found that there was a certain correlation between the rising angle from the bottom of the concave portion of the convex portion constituting the grain, the ratio of the average height of the irregularities to the maximum height of the irregularities of the grain, and white blur. (See FIGS. 5 and 6 described later). On the other hand, no correlation was found between white blurring and other parameters relating to other grain shapes such as grain depth, and parameters relating to grain characteristics such as gloss value (see, for example, FIG. 8 described later).

  Moreover, when the relationship between the direction in which white blur is visually recognized and the injection molding conditions is verified, the direction in which white blur is visually recognized is opposite to the flow direction (filling direction) of the molten resin in the cavity during injection molding. It turns out that.

  From the above verification results, it is assumed that white blur occurs based on the following mechanism. That is, as shown in FIG. 4, at the time of injection molding, first, solidification occurs on the embossed molding surface 12 of the molding die 11 to form a surface solidified layer 13 called a skin layer. Then, the molten resin is continuously filled with a predetermined holding pressure, so that the surface solidified layer 13 formed on the embossed molding surface 12 flows in the flow direction (filling direction) of the molten resin in the cavity 14 indicated by an arrow in FIG. ) In the direction along. At this time, the surface solidified layer 13 moves so as to be dragged on the embossed molding surface 12, so that the dragged surface solidified layer 13 is on the side wall portion 15 on the front side in the filling direction of the embossed molding surface 12 or its corner portion 16. Pressed against and scratched. Therefore, it is considered that when the damaged part is viewed from the front after molding (when the molded product is viewed from the direction corresponding to the right side in FIG. 4), a white blurred part (white blur) appears. .

  Accordingly, if white blur is generated based on the above-described mechanism, the surface solidified layer 13 solidified on the textured molding surface 12 is not easily dragged by the holding pressure of the molten resin (the surface solidified layer 13 on the textured molding surface 12). It is inferred that a grain having a shape that is easily caught) is effective in preventing white blurring. That is, from the above verification results, the surface solidified layer has a holding pressure or the like as the rising angle from the bottom surface of the convex portion constituting the texture increases, and as the ratio of the uneven average height to the maximum uneven surface height of the texture increases. As a result, it is considered that the occurrence of white blur is suppressed.

  The present invention was made on the basis of the above knowledge, and based on the correlation obtained as described above, the rising angle from the bottom surface of the convex portion constituting the texture, and the unevenness with respect to the maximum height of the uneven surface of the texture Since the ratio of the average height is set in a range where no white blur is seen in the texture, and the texture is designed based on the set value, the occurrence of white blur can be prevented in the molding stage. . This eliminates the trouble of reworking the molding die for each molded product and the painting process for concealing the white blur appearing in the wrinkles, thereby reducing the number of man-hours and thus reducing the cost. In the future, as the resin molded products become thinner (lighter), it is necessary to increase the injection speed and holding pressure more than ever, and surface solidification will be promoted. Highly prominent, but by setting the parameters related to the above two types of wrinkle shapes in a range where white blurring is not seen (by determining the wrinkle shape), white blurring occurs while achieving thinning It is possible to mold a resin molded product having a texture that does not.

  In this case, specifically, in the embossing design process, the rising angle of the projecting portion from the bottom surface of the recess is set to 30 ° or more, and the ratio of the unevenness average height to the maximum unevenness height of the embossing is set to 0.6 or more. Is good.

  This is set based on the experimental results to be described later. More specifically, by designing the embossing so that the embossed shape of the molded product is included in the above numerical range, more specifically, the embossing surface of the corresponding molding die. By designing and injection-molding using this, it is possible to mold a resin molded product in which white blur does not occur reliably with respect to the type of resin molded product that has obtained the above correlation.

  As described above, according to the method for manufacturing a resin molded product according to the present invention, it is possible to easily manufacture a resin molded product having a texture that does not cause white blurring without requiring reworking of a molding die or painting after molding. be able to.

It is a principal part expanded sectional view of the resin molded product which concerns on one Embodiment of this invention. It is a principal part expanded sectional view of the molding die for demonstrating notionally the behavior in the cavity at the time of carrying out the injection molding of the resin molded product which has a crimp by the manufacturing method which concerns on one Embodiment of this invention. It is a principal part expanded sectional view of the shaping | molding die for demonstrating notionally the behavior in the cavity at the time of injection-molding the resin molded product which has a crimp with the manufacturing method which concerns on other embodiment of this invention. It is a principal part expansion perspective view of the molding die for demonstrating notionally the behavior in the cavity at the time of carrying out the injection molding of the resin molded product which has a crimp by the conventional manufacturing method. It is a graph as an experimental result which shows the correlation with one parameter regarding the embossed shape which concerns on this invention, and the presence or absence or generation | occurrence | production of the white blurring. It is a graph as an experimental result which shows the correlation with the other parameter regarding the embossed shape which concerns on this invention, and the presence or absence or generation | occurrence | production of the white blurring. It is a graph which clarifies the range where white blurring does not generate | occur | produce about two types of parameters regarding the embossed shape which concerns on this invention. It is a graph as an experimental result which shows the correlation with the other parameter regarding a wrinkle shape, and the presence or absence or generation | occurrence | production of the white blurring.

  Hereinafter, an embodiment of a method for producing a resin molded product according to the present invention will be described with reference to the drawings.

  FIG. 1: has shown the principal part expanded sectional view of the resin molded product 1 obtained by the manufacturing method which concerns on this invention. The resin molded product 1 is, for example, an instrument panel of an automobile, and is provided with an embossed body 2 at least on an upper surface portion (a portion visible from the windshield side). Here, the texture 2 constitutes a minute uneven pattern, and is formed by alternately forming a plurality of convex portions 3 and concave portions 4 as shown in FIG. Further, the convex portion 3 is partitioned from the concave portion 4 by a side surface portion 5 rising from the bottom surface of the concave portion 4 to the top surface of the convex portion 3 at a predetermined angle θ.

  The texture 2 having the above shape is molded simultaneously with the injection molding of the resin molded product 1. At this time, depending on the shape of the texture 2, an area where the texture 2 is formed may be formed in a predetermined direction of the resin molded product 1 (here, For example, white blur may appear when viewed from the front glass side of the instrument panel. Here, as the shape parameter of the texture 2 related to the occurrence of white blur, the rising angle θ from the bottom surface of the recess 4 of the projection 3 constituting the texture 2 and the average roughness r of the roughness 2 with respect to the maximum unevenness d of the texture 2 Ratio R (= r / d). Here, the rising angle θ of the convex portion 3 indicates the inclination angle of the rising portion of the side surface portion 5 with respect to the bottom surface of the concave portion 4, as shown in FIG. The maximum unevenness height d of the texture 2 is substantially equal to the depth of the texture 2 and indicates the shortest distance from the bottom surface of the recess 4 to the top surface of the projection 3 as shown in FIG. And the uneven | corrugated average height r is an area of the part (part shown by cross hatching) enclosed by the virtual line which passes along the bottom face of the recessed part 4 shown with a dashed-dotted line and the outline of the convex part 3 in the cross section shown in FIG. The value obtained by dividing the area by the distance in the width direction (left-right direction in FIG. 1) of the number of the convex portions 3 and the concave portions 4 obtained is shown. The actual thickness of the resin molded product 1 is in mm, whereas the thickness of the texture 2 (the height of the convex portion 3 and the concave portion 4 constituting the texture 2) is as small as μm. However, in order to facilitate understanding, in FIG. 1, the dimension in the thickness direction of the texture 2 is drawn larger than the thickness dimension of the resin molded product 1. The same applies to FIGS.

  It is known from experimental results to be described later that the larger the above-mentioned shape parameters, the less likely white blur appears as a result or the less white blur occurs. This is presumably due to the reasons described below. That is, as shown in FIG. 2, the rising angle θ ′ of the portion corresponding to the side surface portion 5 of the embossed molding surface 12 of the molding die 11 has a magnitude according to the rising angle θ of the resin molded product 1. Therefore, after the start of injection, the surface solidified layer 13 solidified on the embossed surface 12 of the molding die 11 continues along the flow direction of the molten resin (the direction indicated by the arrow in FIG. 2) filled in the cavity 14. When the drag direction is received from the molten resin, the surface solidified layer 13 is more easily caught on the side surface portion 5 rising from the bottom surface of the recess 4 as the rising angle θ of the resin molded product 1 is larger. As a result, it is considered that displacement (dragging) of the surface solidified layer 13 as shown in FIG. 4 is suppressed or prevented. Further, as the ratio R of the average unevenness height r to the maximum unevenness height d in the resin molded product 1 is larger, as shown in FIG. 3, the maximum unevenness height d ′ on the embossed molding surface 12 of the molding die 11 is shown. The ratio R ′ of the uneven average height r ′ is also increased. Therefore, the area where the surface solidified layer 13 is hooked on the side surface portion 5 is increased, and in this case as well, as a result, it is considered that dragging of the surface solidified layer 13 as shown in FIG. 4 is suppressed or prevented. This is because if the surface solidified layer 13 is not dragged, the surface solidified layer 13 is not pressed against the side surface portion 5 of the embossed molding surface 12 or the corner portion with the bottom surface portion of the concave portion 4 to be damaged.

  Therefore, first, the rising angle θ from the bottom surface of the concave portion 4 of the convex portion 3 constituting the texture 2, the ratio R of the uneven average height r to the maximum uneven height d of the texture 2, and the white blur appearing in the texture 2 Correlation with the degree is obtained (correlation obtaining step), and based on the obtained correlation, the rising angle θ of the convex portion 3 from the bottom surface of the concave portion 4 and the ratio of the concave / convex average height r to the concave / convex maximum height d R is set in a range where white blur is not seen in the texture 2 (optimum value setting step). Then, by designing the texture 2 based on the values of θ and R set in this way (texture design process), the resin molded product 1 having the texture 2 that does not cause white blur in any direction is obtained. It can be manufactured by injection molding. More specifically, θ ′ and R ′ for the embossed surface 12 of the molding die 11 are determined based on the values of θ and R set as described above, and embossing is performed based on the values of θ ′ and R ′. The textured surface 12 is formed by setting conditions (for example, masking pattern, etching time, concentration, etc.). Then, by performing injection molding with the molding die 11 having the textured surface 12, the resin molded product 1 having the texture 2 that does not generate white blur can be obtained. According to this method, since the occurrence of white blur can be prevented in the molding stage, it is troublesome to rework the molding die 11 every time the shape of the resin molded product 1 is slightly changed, and the white that appears in the texture 2. The painting process for hiding the blur can be omitted, and man-hours can be reduced and the cost can be reduced. In this case, the optimum range of the ratio R of the rising angle θ and the average height of irregularities is given by θ ≧ 30 ° and R ≧ 0.6 from the experimental results described later (see, for example, FIG. 7). it can. In this way, by obtaining a correlation according to the type of molded product and determining the optimum values (values within the optimum range) of the two types of shape parameters based on this correlation, all resin moldings of the same kind are determined. The present invention can be applied to a product (for example, an instrument panel).

  In the above-described embodiment, the parameters regarding the two types of the embossed shape such as the rising angle θ of the projecting portion 3 and the ratio R of the unevenness average height r to the asperity maximum height d are set to be appropriate so that the embossed 2 does not have white blurring. However, in addition to this, for example, by further flattening the bottom surface shape of the recess 4, the formation of the embossed molding surface 12 of the molding die 11 has been described based on the set value. However, it has been found that the occurrence of white blur can be suppressed or prevented. Therefore, for example, in the case of the texture 2 having a rough bottom surface of the recess 4 (large unevenness), in addition to the above θ and R, the surface roughness Ra of the bottom surface of the recess 4 is reduced to make the texture 2 white blur. By setting it in a range in which no blur is seen, the occurrence of white blur can be prevented at the molding stage.

  Moreover, although the case where this invention was applied when the resin molded product 1 used as the object of forced demolding was used as an instrument panel was illustrated in the above description, it is not limited to this component in particular. For example, the present invention can also be applied to resin-made vehicle interior parts such as a large resin molded product other than the instrument panel such as a door trim and a small resin molded product such as a garnish. Further, the present invention can be applied to resin molded products other than vehicle interior parts as long as they are injection-molded products provided with the texture 2.

  Hereinafter, an experiment conducted by the present inventors to demonstrate the usefulness of the present invention will be described. In this experiment, five kinds of parameters related to the wrinkle shape and wrinkle characteristics, specifically, the wrinkle depth d (= the maximum height d of the wrinkles constituting the wrinkle) and the wrinkle average height of the wrinkles White blur occurs when the ratio R of the height, the area ratio between the convex part and the concave part (when the grain formation area is viewed in plan), the rising angle θ of the convex part from the concave bottom surface, and the gloss value are changed. The presence or absence or the degree thereof was evaluated by a sensory evaluation test, and the presence or absence of correlation between each parameter and white blur was examined.

Specifically, after measuring the above-mentioned parameters of a plurality of types of embossing, injection molding is performed using a molding die provided with a molding surface for molding each embossing, and the resulting resin molded product has an embossing area. Sensory evaluation was performed on the degree of white blur that appeared. The thickness of the portion of the resin molded product where the texture is formed is 1.5 mm. The injection molding conditions were set as follows except that the pressure holding time was changed in three stages (1 s, 2 s, 3 s) based on the settings when the instrument panel was injection molded.
Injection speed: 15mm / s
Injection time: 4.28s
Injection holding pressure switching position: 66 mm
Holding pressure: 500 kg / cm2
Cooling time: 10s

  Experimental results are shown in FIGS. Among these, FIG. 5, FIG. 6, and FIG. 8 all show the results in the case of the pressure holding time 3s. Moreover, the vertical axis in these figures is further quantified by ranking the degree of white blurring (ease of visibility) that appears when the texture provided on the surface of the molded product is viewed from a predetermined direction by sensory evaluation. The higher the score, the higher the degree of white blur (easier to see), and the lower the score, the lower the degree of white blur (hard to see). First, as shown in FIGS. 5 and 6, the rising angle θ of the convex portion constituting the embossed surface from the bottom surface of the concave portion, the ratio R of the average height of the unevenness to the maximum height of the unevenness of the embossing, and the occurrence of white blurring There was a certain correlation with each other. That is, it has been found that as the rising angle θ increases and as the ratio R of the uneven average height to the maximum uneven height of the wrinkles increases, the white blurring is less likely to appear (not easily appear). On the other hand, regarding the depth d of the grain, the gloss value, and the area ratio between the convex part and the concave part, no particular correlation was recognized with the degree of white blur. As an example, FIG. 8 shows a graph showing the relationship between the grain depth d and the degree of white blur. In this case, the rising angle θ that is obtained by sensory evaluation and is recognized as being not worried about white blur (substantially invisible under normal conditions) is 30 ° or more, and the average height of the unevenness relative to the maximum height of the unevenness. The ratio R was 0.6 or more. From this, it has been found that the optimum θ and R can be set within the range indicated by the hatched portion in FIG.

DESCRIPTION OF SYMBOLS 1 Resin molded product 2 Wrinkle 3 Convex part 4 Concave part 5 Side part 11 Molding die 12 Wrinkle shaping surface 13 Surface solidification layer 14 Cavity d Wrinkle depth (maximum unevenness height)
r Convex average height θ Rising angle of convex part from concave bottom

Claims (2)

When manufacturing a resin molded product with a texture on a predetermined surface by injection molding,
Correlation acquisition for acquiring the correlation between the rising angle of the convex portion constituting the grain from the bottom surface of the concave part and the ratio of the average height of the irregularities to the maximum height of the irregularities of the grain and the degree of white blur appearing in the grain. Process,
Based on the correlation obtained in the correlation obtaining step, the rising angle of the convex portion from the bottom surface of the concave portion, and the ratio of the average height of the unevenness to the maximum height of the unevenness of the texture, a range where white blur is not seen in the texture. The optimum value setting process to be set to
A method for manufacturing a resin molded product having a texture, comprising: a texture design process for designing the texture based on the value set in the optimum value setting process.   2. The unevenness design step according to claim 1, wherein, in the embossing design step, the rising angle of the projecting portion from the bottom surface of the recess is 30 ° or more, and the ratio of the uneven average height to the maximum unevenness of the embossment is 0.6 or more. A method for producing a resin molded product having a texture.

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